Debating the Precautionary Principle

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Editor’s Choice Series on Agricultural Ethics

Debating the Precautionary Principle: “Guilty until ProvenInnocent” or “Innocent until Proven Guilty”?

Henk van den Belt*

Applied Philosophy Group, Wageningen University and Research Centre, 6706 KN Wageningen,The Netherlands

On May 20, 1999, Nature published a brief report onan experiment performed by researchers at CornellUniversity that indicated that pollen from geneticallymodified (GM) Bt corn (Zea mays) could kill the lar-vae of monarch butterflies (Danaus plexippus). In lab-oratory tests, caterpillars fed milkweed ( Asclepiascurassavica) leaves dusted with pollen from a Bt corn

hybrid showed retarded growth and increased mor-tality. “These results,” the authors stated, “have po-tentially profound implications for the conservationof monarch butterflies” (Losey et al., 1999). In a pressrelease announcing the publication in Nature, theprincipal investigator on the Cornell study, JohnLosey, had expressed due caution: “Pollen from Bt-corn could represent a serious risk to populations of monarchs and other butterflies, but we can’t predicthow serious the risk is until we have a lot more data.And we can’t forget that Bt-corn and other transgeniccrops have a huge potential for reducing pesticideuse and increasing yields. This study is just the firststep, we need to do more research and then objec-tively weigh the risks versus the benefits of this newtechnology” (Cornell News, 1999). Such caution waswasted on Greenpeace International. The day thefindings of the Cornell study were published it al-ready demanded that authorities in the United States,Argentina, Canada, and the European Union takeimmediate action and prohibit the growing of genet-ically engineered maize crops. The environmentalistnongovernmental organization (NGO) reiterated itsearlier call for a ban on all releases of geneticallymodified organisms (GMOs). Less than a monthlater, in a media-oriented action, members of Green-peace dressed up as butterflies confronted a meeting

of European Union environment ministers held inLuxembourg, carrying banners demanding “Give

butterflies a chance.” In Europe, their campaign ap-parently found resonance among the authorities: TheEuropean Commission decided to freeze the ap-proval process for new Bt maize varieties.

The Cornell study did not show that monarch but-terfly populations in the wild were actually endan-gered by Bt corn. However, when Monsanto andNovartis, the companies that sold Bt corn at thattime, correctly pointed out that the detrimental ef-

fects had so far only been shown in the laboratory,Greenpeace branded them as irresponsible. Aspokesperson declared: “Such reactions are the pre-cise opposite to precaution and follow the same pat-tern of denial these companies have employed fordecades, when health and environmental effects of their chemical pesticides were exposed. However, inthe case of these GMOs we are talking about livingtoxins that can reproduce in nature and transmittheir dangerous traits to wild species. We cannotconsider GMOs harmless until harmful effects arefully proven (sic)” (Greenpeace, 1999a). (The last sen-tence is obviously a—Freudian?—slip of the tongueand should be read: “We cannot consider GMOsharmless until the absence of harmful effects is fullyproven.”) For Greenpeace, not just monarchs weresupposed to be endangered. The NGO drew up a listof over 100 species of butterflies that it believed could

be harmed by GM maize. It accused biotech compa-nies and regulatory authorities of fully ignoring theserisks (Greenpeace, 1999b). More recent field research

performed in the American Midwest, however,seems to indicate that monarch butterfly populationsare hardly affected, if at all, by the large-scale culti-vation of Bt maize in this region (Ortman et al., 2001).

The monarch butterfly case is only one amongmany occasions in which the so-called PrecautionaryPrinciple (PP) has been invoked to advocate preven-tative action to forestall possible harm even beforethe likelihood or the possible extent of the latter has

been scientifically well established. This principle ishighly contested. With many other environmentalistNGOs, Greenpeace champions its adoption as a cen-tral principle of international law against tenacious

opposition from the United States, Canada, and Aus-tralia (Greenpeace, 2002). The principle is also atissue in recent World Trade Organization trade dis-putes between the United States and the EuropeanUnion. But why does the PP play such a central role?

PRECAUTIONARY PRINCIPLE

The PP is an outgrowth of increased environmen-talist awareness since the 1970s. The conviction tookhold that humanity finds itself in a historically un-precedented situation in which our technological ca-pacity and the potential scale of our actions far ex-

ceed our predictive knowledge. According to the

* E-mail [email protected]; fax 31–317–485453.

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German philosopher Hans Jonas, this discrepancy between the ability to foresee and the power to actitself assumes ethical importance and asks for humil-ity and responsible restraint on our part. Jonas main-tains that it is possible to extract from this situation of profound scientific uncertainty a rule or principle of decision making that is itself not uncertain at all,namely the rule “to give in matters of a certain mag-nitude—those with apocalyptic potential—greaterweight to the prognosis of doom than to that of bliss”(Jonas, 1984). The supreme moral imperative in thenew age, Jonas holds, is that humankind may not putits own existence and survival at stake in the wagerof technological progress.

If we want to find a philosophical basis for the PP,we must look for it in Jonas’ book on the imperativeof responsibility (although he himself did not use theexpression PP). Environmentalists often hold thatmodern biotechnology has “apocalyptic potential”

because it tampers with the basic processes of life. If we release GMOs into the environment, the ultimateconsequences for the natural flora and fauna areextremely hard to predict but may well be irrevers-ible. However, many environmentalists, just like Jo-nas, believe that we possess a decision rule or prin-ciple for dealing with fundamental scientificuncertainty that is itself not the least uncertain. Thatrule is the PP. Thus, in almost any debate, it seemsthat the PP can be brought in as a trump card tooverride all other considerations and arguments. Butwhat exactly is the PP?

Proponents of the PP assert that the principle is

already “enshrined” in such international agree-ments as the Convention on Biological Diversity andthe Cartagena Protocol on Biosafety, but existing def-initions of it are at best partial and incomplete. In thecontext of dealing with environmental hazards, theRio Declaration of 1992 presented the following for-mulation of what a precautionary approach entails:“Where there are threats of serious or irreversibledamage, lack of full scientific certainty shall not beused as a reason for postponing cost-effective mea-sures to prevent environmental degradation.” Awell-known definition of the PP was spelled out in a

January 1998 meeting at Wingspread in Racine, Wis-

consin. The Wingspread Statement summarized theprinciple thus: “When an activity raises threats of harm to human health or the environment, precau-tionary measures should be taken even if some causeand effect relationships are not fully established sci-entifically” (Raffensberger and Tickner, 1999). Defi-nitions such as these beg many questions. Is thereever full scientific certainty? Do we need a minimalthreshold of scientific certainty or plausibility beforewe may (or should) undertake preventative action?And do we really know how to prevent harm if weare so much ignorant about the underlying cause-effect relationships? The definitions that are cur-

rently on offer fail to spell out the precise conditions

that have to be fulfilled before the PP may be invokedor the nature of the preventative action that has to betaken. The types of action suggested range from im-plementing a ban, imposing a moratorium while fur-ther research is conducted, allowing the potentiallyharmful activity to proceed while closely monitoringits effects, to just conducting more research. The PPdoes not have a very precise meaning as long as suchcrucial aspects are left largely unanswered.

In practice, however, the PP is often given a moredefinite meaning by reducing it to an absurdity. Nor-mally, no minimal threshold of plausibility is speci-fied as a “triggering” condition, so that even theslightest indication that a particular product or activ-ity might possibly produce some harm to humanhealth or the environment will suffice to invoke theprinciple. And just as often no other preventativeaction is contemplated than an outright ban on theincriminated product or activity. The intervention of

Greenpeace in the monarch butterfly case seems to fitthis pattern.

Closely linked to various versions of the PP is theidea of reversing the onus of proof. Thus, the adher-ents of the Wingspread Statement declare that “theapplicant or proponent of an activity or process orchemical needs to demonstrate that the environmentand public health will be safe. The proof must shift tothe party or entity that will benefit from the activityand that is most likely to have the information”(Raffensberger and Tickner, 1999). Greenpeace alsoholds that effective implementation of the PP re-quires a shift in the burden of proof (Greenpeace,

2001). Shifting the burden of proof seems a fairlystraightforward way to ensure, as Jonas demanded,that greater weight will be given to the “prognosis of doom” than to the “prognosis of bliss.”

THE LOGIC OF PASCAL’S WAGER

Before looking into the proper assignment of the burden of proof, we must first examine more closelythe underlying justification for the strong version of the PP. Why should the prospect of harmful effects of a new technology take precedence over the prospectof beneficial effects, quite apart from the inherentlikelihood of each of these possibilities? The obviousanswer seems to be that such a priority is defensibleonly when the harmful effects are of such magnitudethat they carry catastrophic (or, as Jonas would say,“apocalyptic”) potential. The infinite costs of a pos-sible catastrophic outcome necessarily outweigheven the slightest probability of its occurrence.

This type of reasoning exhibits a remarkable resem- blance to a well-known example of a “zero-infinitydilemma,” namely Pascal’s famous “wager.” When itcomes to wagering on the existence of God, the 17thcentury French philosopher argued incisively in hisPensees that it is better to be safe than sorry (Haller,

2000; Graham, 2002; Manson, 2002). Given an un-

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known but nonzero probability of God’s existenceand the infinity of the reward of an eternal life, therational option would be to conduct one’s earthly lifeas if God exists.

Alas, Pascal’s reasoning contains a fatal flaw. Hisargument is vulnerable to the “many gods” objection(Manson, 2002). Consider the possible existence of another deity than God, say Odin. If Odin is jealous,he will resent our worship of God, and we will haveto pay an infinite price for our mistake. Never mindthat Odin’s existence may not seem likely or plausi-

ble to us. It is sufficient that we cannot exclude thepossibility that he exists with absolute certainty.Therefore, the very same logic of Pascal’s wagerwould lead us to adopt the opposite conclusion not toworship God. Pascal’s argument, then, cannot bevalid.

If the wager argument is not valid, the strong ver-sion of the PP (which Manson dubs the “catastrophe

principle”) cannot be valid either. Take the applica-tion of this principle to the problem of global warm-ing. Environmentalists often argue that even if it isnot conclusively established that the emission of car-

bon dioxide and other gases causes an enhancedgreenhouse effect, the mere prospect of an ecologicalcatastrophe due to such a scenario should lead us todrastically curb our emissions of greenhouse gasesnow. By the same logic, however, one could conjureup the possibility of a coming ice age. The mereprospect of this equally catastrophic scenario shouldthen induce us to avert this outcome by stepping upthe emission of greenhouse gases. Thus, the strong

version of the PP would lead to contradictory recom-mendations (compare with Graham, 2002). In a sim-ilar way, it could be argued that this principle com-mits us to each of two contradictory policies: (a) Wemust not develop GM crops, and (b) We must de-velop GM crops. The first alternative is argued vehe-

mently by many environmentalists who appeal to thePP. To support the second possibility, Gary Com-stock conjures up a dramatic scenario in which peo-ple are forced to seize upon the remaining reserves of nature in a desperate effort to overcome food short-ages resulting from global warming. He then argues,in the style of the environmentalists, that “lack of fullscientific certainty that GM crops will prevent envi-ronmental degradation shall not be used as a reasonfor postponing this potentially cost-effective mea-sure” (Comstock, 2000).

BURDENS AND STANDARDS OF PROOF

Therefore, the strong version of the PP is untena- ble. But what about the proposed shifting of the onusof proof toward those who advocate a new technol-ogy or activity? Reversing the burden of proof wouldamount to substituting the maxim “guilty until

proven innocent” for the age-old legal principle “in-nocent until proven guilty.” Biotech enthusiasts andantiregulationists resent this departure from whatthey consider time-honored legal sanity (Miller andConko, 2000). They are prone to counter the frequentinvocation of the PP with an equally insistent de-mand of “sound science.” The same opposition isalso at the center of the present World Trade Orga-nization trade disputes between the United Statesand the European Union and their disagreement onthe regulation of GM crops. One side claims themoral high ground, whereas the other side attemptsto seize the scientific high ground. The situation is

highly polarized because various economic and po-litical interests are at stake (Fig. 1).The critics of the PP assert that the burden that

environmentalists and regulators want to impose onthe proponents of new technologies tends to be un-

bearable (Miller and Conko, 2000). In the name of

Figure 1. Wheat (Triticum aestivum ) fields inthe Palouse region of the state of Washington inthe United States. The polarized discussionabout the PP and the adoption of GM crops hasbecome a proxy for everything that Europeansand environmentalists in other countries don’t

like about modern agriculture. The rejection of agricultural biotechnology may perhaps be tol-erated as a European indulgence but hardlymakes sense on a global scale.

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absolute safety, the latter are asked nothing less thanto demonstrate conclusively that the new technolo-gies they advocate offer no possible harm. This is aformidable, perhaps even logically impossible, task.You cannot prove a negative (compare with Wil-davsky, 1995). Moreover, a risk-free world is not areal option. Thus, a consistent application of the PPwould in the final analysis stifle all innovation.

A closer analysis of what is involved in applyingthe classical principle “innocent until proven guilty,”however, reveals that the situation need not be as

black and white as it seems at first sight. Take theparadigm case of criminal justice. There are two mainways in which a miscarriage of justice can comeabout. Either the suspect did not commit the crime,

but the verdict found him guilty; or the suspect didcommit the crime, but the verdict found him notguilty. In a civilized system of justice, the risks of thefirst type of error are minimized as far as possible.That is what is meant by the phrase “innocent untilproven guilty.” The system contains safeguards andprecautions in the form of high standards of proof soas to ensure that a suspect will be condemned for acertain criminal offense only if it has been established“ beyond reasonable doubt” that he in fact committedthe alleged offense. Alas, there is a price to be paidfor this cautious and civilized approach, namely thepossibly large number of wrongdoers who have to beacquitted due to “lack of sufficient proof.” To a cer-tain extent, the risks of the two types of error areinversely related. We may try to reduce the risk of condemning an innocent person by demanding ever

more exacting standards of proof but only at theexpense of increasing the risk of acquitting culpableoffenders. Therefore, we must recognize that there isan inevitable trade-off involved in the design of oursystem of criminal justice. We may attempt to set ourstandards as high as we can, but somewhere a bal-ance must be struck, lest the system will becomeunworkable by making it too difficult to pass sen-tence on the majority of wrongful offenders. (In sta-tistical testing, there is a similar trade-off to be made

between the chances of committing a type I or a typeII error, i.e. rejecting the null hypothesis of “no ef-fect” when it is in fact true or failing to reject the null

hypothesis when in fact it is false. By selecting asignificance level, we implicitly strike a particular

balance. Ideally, this balance should depend on ourestimation of the costs—economic and other—asso-ciated with either of the two types of error.)

The above analysis shows that the matter at issue isnot just where to place “the” burden of proof. Assoon as we allow for more or less exacting standardsof proof, an extra dimension of variation immedi-ately becomes visible. In other words, the burden wewant to put on the shoulders of one or the other party

becomes more or less heavy depending on whetherwe set our standards of proof more or less highly.

This consideration may help us to escape from the

unduly polarized opposition of PP versus soundscience.

In most countries, companies aiming to commer-cialize GM crops have to submit their products toscrutiny for health effects and environmental im-pacts. This scrutiny can be more or less searching.The ideal of those who swear by “sound science” is afully quantified risk assessment. However, it is onlypossible to meet this objective in more limited con-texts, where direct and short-term hazards such astoxicity or pathogenicity are at issue. Even then theexpression “sound science” is disingenuous becauseit obscures the extra-scientific value judgments thatnecessarily enter into the whole exercise (e.g. identi-fication of hazard types, baselines of acceptability,and trade-offs between type I and type II errors). Inother contexts, where indirect, cumulative, or moresubtle ecological effects are at issue, the format of the

fully quantified risk assessment is unattainable. Ad-herents of “sound science” will be tempted to down-play such less straightforward hazards as purely hy-pothetical, conjectural, or theoretical risks that cansafely be ignored. However, as the proponents of thePP are never tired in pointing out, lack of evidence of harm is not evidence of lack of harm. If we are reallyconcerned about such hazards, we can put in addi-tional investigative effort to learn more about theirplausibility or likelihood. It would be absurd to haltour inquiries with an appeal to “sound science.”

THE FUTURE OF WORLD AGRICULTURE

A recent European directive on the deliberate re-lease of GMOs into the environment lays down thatany company that wants to introduce or commercial-ize a transgenic crop should carry out a “full” envi-ronmental risk assessment taking into account “di-rect, indirect, immediate and delayed effects” (EC,2001). This new regulation of GM crops goes muchfurther than current US registration requirements,although some American biologists also argue for amore comprehensive approach (Obrycki et al., 2001).

The new European Directive surely places a heavy

burden of proof on biotech companies intending tointroduce GMOs. Whether or not they are able totake that burden on their shoulders will partly de-pend on the definition of a standard protocol ormethodology for conducting environmental risk as-sessments. The danger to be avoided is that the ob-ligations imposed on these companies will become“open-ended,” putting them entirely at the mercy of regulatory agencies and NGOs asking for ever-escalating assurances of environmental safety. Thissuspicion will be enhanced by the fact that the draft-ing of the Directive has avowedly been informed bythe PP and that regulatory authorities may give con-

sent to the introduction of GMOs only after they have

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been satisfied that the release will be safe for humanhealth and the environment.

The fairly comprehensive scope of the requiredenvironmental risk assessment need not be offensivein itself, if rules of fair play for the regulation of GMcrops can be developed. More clarity is also neededabout the societal values that have to be taken intoaccount in evaluating risks. The outcome of the as-sessment is clearly contingent, for instance, onwhether or not chemical-intensive methods in agri-culture are taken as a normative baseline or whetheror not a strong commitment to organic agriculture asa viable option is maintained (Levidow, 2001). Thepros and cons of a Bt maize hybrid or any othertransgenic crop might be quite different in Europethan in the United States. Europeans are usuallystrongly attached to farmland because their countrieslack vast tracts of national parks and other “wilder-ness” areas. Willy de Greef, head of regulatory affairs

at Syngenta Seeds, holds that the debate in Europe onGM foods is not fundamentally about safety, but is infact a proxy for a larger debate on how farmingshould be done (Hileman, 2001). GM crops have

become a symbol for all that Europeans don’t like inmodern agriculture.

Although a passion for organic farming and a rejection of agricultural biotechnology perhaps may betolerated as a European indulgence, the prospecthardly makes sense on a global scale. Yet, this isprecisely what Greenpeace International offers us asa worldwide “solution.” I think the NGO owes us adeadly serious answer to the difficult question of

how to feed a growing world population and sustainnatural biodiversity without using the tools of mod-ern biotechnology (compare with Trewavas, 1999).We can even press the environmentalist organization

by invoking the PP!Thus, it appears that the polarized debate on the PP

is just a proxy for a larger debate on the future of world agriculture.

Received March 13, 2003; returned for revision April 2, 2003; accepted April

2, 2003.

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Debating the Precautionary Principle